Plasma arc torches have heretofore been commercially provided for cutting or welding and conventionally include a torch handle, a torch head attached thereto, a generally elongate electrode insertable in the torch head, current supply means adapted to be connected to a main power supply for supplying an electrical current through the torch handle to the torch head, gas flow means adapted to be connected to a source of gas for supplying a flow of the gas through the torch head for the plasma arc created by the torch and in contact with a lower portion of the electrode for partial cooling of the electrode, a current transfer assembly in the torch head for receiving and seating therewithin at least an upper portion of the electrode against upward movement in the torch head and operatively connected to the current supply means for transferring current to the electrode, a nozzle assembly for receiving and seating the lower portion of the electrode against downward movement in the torch head and operatively connected with the gas flow means for issuing a plasma arc outwardly from the torch head. The plasma arc is developed by passing the arc and gas through an arc constricting passageway formed in the nozzle located between the electrode and the work being cut or welded. This plasma arc cutting or welding process is well known to those with ordinary skill in the art and does not require further explanation herein for an understanding of the present invention. An example of this type of plasma arc cutting or welding torch, with safety control means, is disclosed in U.S. Pat. No. 4,580,032, issued Apr. 1, 1986, and assigned to the assignee of the present application.
This type of plasma arc torch, as may be seen in this prior U.S. Pat. No. 4,580,032, utilizes passageways through the torch head for the flow of gas for the plasma arc and for partial electrode cooling. These passageways are conveniently formed, in part, in the current transfer assembly, but do not pass in contact with the upper portion electrode being seated in the current transfer assembly so as not to interfere with seating of the upper part of the electrode in the current transfer assembly and contact thereof with the electrode for transferring current to the electrode.
Due to the extremely high temperatures caused by the plasma arc, the life of the electrodes is very short and the electrodes must be frequently replaced. Even though the plasma arc torch, as disclosed in prior U.S. Pat. No. 4,580,032, utilizes a reversible construction for the electrode in which the electrode can be removed and reversed and partial cooling for increasing the life of the electrode, the problem of frequency of replacement of the electrode still exists.